Fabrication And Characterization Of Resistive Switching Based On ZnO Films

With the rapid development of integrated circuits, Flash memory feature sizes continue to shrink. Accordingly the thickness of gate oxide should also be reduced to keep devices function properly. As a result, the tunneling effect appears to be obvious, leading to the increase of the leakage current which deteriorates the reliability of flash devices. On the other hand, the demand for the high-performance memory is gradually increased with the the rapid development of digital high tech, hence it turns to be inevitable that we should find out some new storage mechanisms for the non-volatile memory. At present, a variety of new non-volatile memory have been developed, such as Ferroelectric Random Access Memory (FeRAM), Phase Change Random Access Memory (PCRAM), Magnetoresistive Random Access Memory (MRAM) and Resistive Random Access Memory (ReRAM). Among these, ReRAM has attracted great attention due to rapid operation, low power consumption, simple structure, high-density mass storge, low cost, good compatibility with conventional CMOS process, and is expected to be the next generation universal memory.ZnO is an important compound semiconductor material, which has been widely used in many fields such as solar cells, ultraviolet detectors, varistors, gas sensors owing to its excellent optical and electrical properties and stability. But the research on ZnO thin films used as the resistive switching material started relatively late. Therefore, it is necessary to study its resistive switching characteristics. In this paper, Cu/ZnO/n+-Si sandwich structure devices have been fabricated by magnetron sputtering method. The influences of different process parameters on the properties of the thin films have been studied by x-ray diffractometer, UV-Vis spectrometer, atomic force microscopy, I-V curve tracer and LCR meter etc. Based on the experimental results, the mechanism of resistive switching has also been discussed.The results show that: ZnO thin films fabricated by magnetron sputtering method exhibit reversible and steady unipolar resistive switching behavior, and it's found that the forming voltage and set voltage have linear relationship with the thickness of thin films. The energy required for the rupture of filament in the process of reset is related to the amount of oxygen defects. Besides, the conduction mechanisms dominating the low and high resistive states are Ohmic behavior and Space Charge Limit Current, respectively.The research on ZnO thin films used as the resistive switching material started relatively late, but considering that ZnO is an important compound semiconductor material, which has been widely used in many fields such as solar cells, ultraviolet detectors, varistors, gas sensors due to its excellent optical and electrical properties and stability, therefore, it is necessary to study its resistive switching characteristics. In this paper, Cu/ZnO/n~+-Si sandwich structures have been fabricated by using magnetron sputtering method. The influences of the different process on the properties of the thin films such as resistive switching characteristics, crystalline structure have been studied. On the basis of the experimental results, mechanism of resistive switching has also been discussed.The results show that: ZnO thin films fabricated by magnetron sputtering method exhibit reversible and steady unipolar resistive switching behaviors, and it's found that the forming voltage and set voltage have linear relationship with the thickness of thin films. The energy required for the rupture of filament in the process of reset is related to the amount of oxygen defects. Besides, it's found that the conduction mechanisms dominating the low and high resistive states are Ohmic behavior and Space Charge Limit Current, respectively.